Recording device with automatic gain range changer and d.c. correction means

ABSTRACT

An automatic recording device incorporating a range changer and an asymmetrical DC level correcting means. The range changer automatically selects a gain capable of supplying the recorder, for example, with an electrocardiograph signal of suitable amplitude regardless of the amplitude of the detected electrocardiograph signal. The asymmetrical DC level correcting means corrects the DC level of the recorder so as to center the electrocardiogram on the recording chart.

.[54] RECORDING DEVICE WITH AUTOMATIC GAIN RANGE CHANGER AND D.C.CORRECTION MEANS Inventors: Tomiyoshi Ota; Katunobu Takigawa; MasasadaHonda, all of Tokyo, Japan Nihon Denshi Kabushiki Kaisha, Tokyo, JapanFiled: May 14, 1971 Appl. No.: 143,552

Assignee:

[30] Foreign Application Priority Data May 16, 1970 Japan ..45/41741[52] U.S. Cl. ..l28/2.06 G, l28/2.06 B, 307/264,

[58] Q Field of Search ..l28/2.06 B, 2.06 G, 2.06 R, 128/205 Q; 330/29,149; 307/264 Int. Cl. ..A61b 5/04 3,699,948 14 1 Oct. 24, '1972 PrimaryExaminer-William E. Kamm Attorney-Webb, Burden, Robinson & Webb [57]ABSTRACT An automatic recording device incorporating a range changer andan asymmetrical DC level correcting means. The range changerautomatically selects a gain capable of supplying the recorder, forexample, with an electrocardiograph signal of suitable amplituderegardless of the amplitude of the detected electrocardiograph signal.The asymmetrical DC level correcting means corrects the DC level of therecorder so as to center the electrocardiogram on the recording chart.

5 Claims, 3 Drawing Figures 1 2 22 2a 5 f J R/WE MAIN HECTOR AHPUF'ER TCHM R AMPLIFIER ,7 T i 6! OT 9 POSITIVE CIRCUIT V PEAK conmmror 22m: TOR

J J PM ENTIAL 70 5- AMPLIFIER W *2 c/Rcu/T age/4 1v: i 2/ M P 70R HECTOR[on AM /8 i J 3 /6 DL. LEVEL CORKECTING EflA/S RECORDING DEVICE WITHAUTOMATIC GAIN RANGE CHANGER AND DO CORRECTION MEANS BACKGROUND OF THEINVENTION This invention relates to a recording device capable ofrecording an electrocardiogram of more or less uniform amplituderegardless of the amplitude of the SUMMARY OF THE INVENTION Briefly, adevice according to this invention detects the positive peak signal andthe negative peak signal of the electrocardiograph signal wave formemanating from the person under examination. It then detects a peak-peaksignal and an asymmetrical DC signal from said positive and negativepeak signals. The gain range of an incorporated range changer isautomatically selected according to said peak-peak signal so as toalways record an electrocardiogram of more or less constant amplitude.The superimposed signals; i.e., the signal passed through the rangechanger and the asymmetrical DC signal, are then fed into a recorder andrecorded.

It is an advantage of this invention to provide a recording device whichoperatesautomatically, which always records an electrocardiogram orsimilar signal pattern at a suitable amplitude and which always recordsthe electrocardiogram so that the portions of theelectrocardiogram aboveand below the center line are more or less equal.

' BRIEF DESCRIPTION OF THE DRAWING The invention will be readilyunderstood by reading the following detailed description made withreference to the attached drawing in which:

FIG. 1 is a block diagram showing one embodiment of this invention;

FIG. 2 is an electrocardiogram used for explanatory purposes; and,

FIG. 3 is a block diagram showing part of another embodiment of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT tive 5 and negative 6 signalpeak are indicated. Broken line 7 indicates themedian position of thetwo max- 2 imum positive and negative peaks. The peak-peak height 8 ofthe electrocardiogram and the half peakpeak height 9 are shown. Thedifference 10 between the mean and median positions; i.e., the amount bywhich the DC level requires correcting and the width of the recordingpaper 11 are also shown.

The preamplified signal is detected by two peak detectors l2 and 13.More specifically, positive peak detector 12 detects the maximumpositive peak value of the signal and negative peak detector 13 detectsthe maximum negative peak value of said signal. The detected outputs ofthe two detectors are then fed into a differential amplifier 14 whichdifferentiates both peak values to obtain the peak-peak value. Next, thedifferentiated output of the differential amplifier 14 is applied to twocomparators 15 and 16 each having standard voltage levels. For the sakeof explanation, we will refer to these two standard voltage levels as Aand B. Now supposing, for example, that A is less than B, the output ofboth comparators will be 0 if the differentiated output from thedifferential amplifier 14 is less than A. Further, if the differentiatedoutput is greater than A but less than B, the output of comparator 15will be l and the output of comparator 16 will be 0. Lastly, if thedifferentiated output is greater than B, the outputs of comparators 15and 16 will be 1. The outputs of comparators are determined by theoutput of the differential amplifier 14 or, in other words, thepeak-peak value of the electrocardiograph signal.

As shown in FIG. 1, by connecting comparator 15 to AND circuit 19 viaNOT circuit 17 and to AND circuits 20 and 21 directly and by connectingcomparator 16 to AND circuits 19 and 20 via NOT circuit 18 and to ANDcircuit 21 directly, the AND circuits operate selectively in accordancewith the value of the aforementioned peak-peak signal.

If the peak-peak value is less than A, AND circuit 19 detects l and ANDcircuits 20 and 21 detect 0. If the peak-peak value is greater than Abut less than B, AND circuit 20 detects l and AND circuits l9 and 21detect 0. If the peak-peak value is greater than B, AND circuit 21detects l and AND circuits 19 and 20 detect 0.

Each AND circuit is connected to one of three gate circuits constitutingrange changer 22, said range changer operating to change the gain rangeby selectively closing one of the gate circuits in accordance with theaforementioned operative sequence. In this way, an electrocardiographsignal of suitable amplitude is fed to main amplifier 23.

Additionally, the junction of resistors R and R connected in seriesbetween the outputs of detectors 12 and 13, is connected to DC levelcorrecting means 24 also consisting of three gate circuits which operatein accord with the range changer gate circuits. In other words, theasymmetrical DC voltage from the junction of resistors R and R isdivided in proportion to the gain range change of the range changer. Asa result, an

I asymmetrical DC voltage between the maximum positive value of thesignal and the maximum negative value of the signal is applied to mainamplifier 23 after being reduced to a suitable level by the DC levelcorrecting means 24.

- In the main amplifier 23, theDC voltage from the DC level correctingmeans and electrocardiograph signal from the range changer aresuperimposed so that the center of the electrocardiogram correspondswith the center of the recording paper of recorder 25 upon which theelectrocardiograph signal is recorded;

' Further, it is also possible to construct the circuit comprisingdifferential amplifier 14, comparator 15, NOT circuit 27 as shown inFIG. 3. In this case, the differentiated output of the difi'erentialamplifier 14 is applied to a comparator 26 having a standard voltagelevel C. The output of the comparator 26 is if the differentiated outputfrom said differential amplifier is less than C. If said output isgreater than C, the output of said comparator is l The output of thecomparator 26 is split, one part being fed to 22 and 24 directly,theother part being fed to said circuits via NOT circuit 27.

In cases where the wave form to be recorded is not unduly asymmetricalor there is sufficient chart paper clearance above and below theelectrocardiogram, the asymmetrical DC voltage may be applied directlyto the main amplifier 23 without passing it through the DC levelcorrecting means 24.

Having thus described the invention with the detail and particularity asrequired by the Patent Laws, what is desired protected by Letters Patentis set forth in the following claims.

l.A recording device comprising a bioelectrode for detecting anelectrocardiograph signal, means for detecting a peak-peak value of saidelectrocardiograph signal, means for changing the range in which gain isautomatically selected in accordance with said peakpeak value so as toobtain an electrocardiograph signal of suitable amplitude regardless ofamplitude of detected electrocardiograph signal, means for detecting anasymmetrical DC signal of said electrocardiograph signal in order torecord an electrocardiogram at the center of the recording paper and a'recorder for recording said electrocardiograph signal passed throughsaid range changer after superimposing said asymmetrical DC signal.

2. A recording device as claimed in claim 1 comprising at least onecomparator having a standard voltage level, said comparator operatingsaid range changer by means of the signal obtained by comparing saidpeakpeak value with said standard voltage level.

3. A- recording device comprising a bioelectrode for detecting anelectrocardiograph signal, means for detecting the positive peak valueand the negative peak value of said electrocardiograph signal, means forobtaining a peak-peak value from said positive peak value and saidnegative peak value, means for changing the range in which gain isautomatically selected in accordance with said peak-peak value so as toobtain an electrocardiograph signal of suitable amplitude regardless ofamplitude of detected electrocardiograph signal, means for detecting anasymmetrical DC signal of said electrocardiograph signal from saidpositive peak value and said negative peak value and a recorder forrecording said electrocardiograph signal passing through said rangechanger after superimposing said asymmetrical DC signal.

4. A recording device as claimed in claim 3 wherein said means fordetecting asymmetrical DC signal comprises two series resistorsconnected between the out-

1. A recording device comprising a bioelectrode for detecting anelectrocardiograph signal, means for detecting a peak-peak value of saidelectrocardiograph signal, means for changing the range in which gain isautomatically selected in accordance with said peak-peak value so as toobtain an electrocardiograph signal of suitable amplitude regardless ofamplitude of detected electrocardiograph signal, means for detecting anasymmetrical DC signal of said electrocardiograph signal in order torecord an electrocardiogram at the center of the recording paper and arecorder for recording said electrocardiograph signal passed throughsaid range changer after superimposing said asymmetrical DC signal.
 2. Arecording device as claimed in claim 1 comprising at least onecomparator having a standard voltage level, said comparator operatingsaid range changer by means of the signal obtained by comparing saidpeak-peak value with said standard voltage level.
 3. A recording devicecomprising a bioelectrode for detecting an electrocardiograph signal,means for detecting the positive peak value and the negative peak valueof said electrocardiograph signal, means for obtaining a peak-peak valuefrom said positive peak value and said negative peak value, means forchanging the range in which gain is automatically selected in accordancewith said peak-peak value so as to obtain an electrocardiograph signalof suitable amplitude regardless of amplitude of detectedelectrocardiograph signal, means for detecting an asymmetrical DC signalof said electrocardiograph signal from said positive peak value and saidnegative peak value and a recorder for recording said electrocardiographsignal passing through said range changer after superimposing saidasymmetrical DC signal.
 4. A recording device as claimed in claim 3wherein said means for detecting asymmetrical DC signal comprises twoseries resistors connected between the outputs of said positive andnegative peak value detecting means and an asymmetrical DC levelcorrecting means for correcting the level of said asymmetrical DC signaldetected at the junction of said two resistors.
 5. A recording device asclaimed in claim 4 wherein said DC level correcting means corrects thelevel of said asymmetrical DC signal in unison with said range changer.